1. Field of the Invention
This invention relates to the improvement of the ammonolytic stability of polyester textile yarn by short term corona discharge treatment at high processing speeds.
2. Brief Description of the Prior Art
Polyester textile cord used in tires suffers from degradation due to the presence of various organic amines normally present in the rubber which are used as curing accelerators. The effect of an organic amine coming into contact with the polyester material is to accelerate the aging process leading to degradation of the polyester polymer chain and, thus, to a loss in the tensile strength of the fiber and subsequent shorter life for the tire. It is known in the art that esters in general are subject to ammonolysis under partial or totally anhydrous conditions, as disclosed in A. R. Day et al., JACS, Vol. 71, p. 1245 (1949), which is essentially the environment that polyester cord experiences within a tire.
Prior art methods have long been known in the film industry for increasing the adhesion of film and improvement of film surface properties by exposing them to an atmosphere of ionizing radiation.
Prior art methods are also known for treating synthetic textile fibers by exposing them to ionizing radiation and electrical discharge in a gas plasma to improve dye receptivity, as described in Belgium Pat. No. 653,113 (Eicken), and also for improving the adhesion of textile fiber cord in tires, where electrical discharge treatment is coupled with an after treatment of a resorcinol-formaldehyde-latex, as described in U.S. Pat. No. 3,477,902 (Tomasino, et al.) and Lawton, J. Appl. Pol. Sci., Vol. 18, p. 1557 (1974).
Electrical discharge treatment of fibers has been described using a rotating arc discharge mechanism which restrains the fiber from lateral displacement to improve the surface properties, as described in British Pat. No. 1,300,088 (Imperial Chemical Industries Ltd.).
Corona discharge treatment of fibers is also known to improve surface properties with respect to adhesion and surface appearance, as exemplified in Japanese Patent 7,010,797 (Asahi Chem. Ind. Co. Ltd.), U.S. Pat. No. 3,817,701 (Thorsen), and Japanese Kokai No. 9,035,692 (Kuraray Co. Ltd.).
However, none of the prior art references teaches the improvement of polyester textile material with respect to resistance to attack by ammonia or organic amines, e.g. ammonolytic stability. Also, prior art processes are mainly concerned with the improvement of adhesion through the application of ionized gaseous atmospheres by electrical discharge which invariably results in a decrease in the tensile strength of the polyester fiber since relatively long exposure times are necessary for significant improvements in polyester fiber adhesion. Further, prior art processes are not adaptable into an overall continuous process for producing polyester yarn which requires rapid processing speeds of at least 100 feet per minute, nor do any of such processes teach the formation of a polyester yarn in which the majority of the individual fibers have improved ammonolytic stability, thus producing an inherently more stable yarn as opposed to one in which the yarn bundle or cord made from the yarn is merely surface treated.
It is an object of this invention to produce polyester yarn possessing improved ammonolytic stability without substantial loss of its tensile strength.
It is also an object of this invention to produce a polyester yarn possessing improved ammonolytic stability at a processing speed which can readily be incorporated into a continuous commercial process for producing polyester yarn requiring very high speeds.
It is a further object to produce a tire cord comprised of polyester yarn possessing improved ammonolytic stability.
It is also a further object to provide a tire comprised of the tire cord produced by the process of this invention.
These and further objects of the invention will become apparent from the disclosure contained herein.